The present invention relates to stack lights, which convey visual and/or audible information regarding operating and/or fault conditions in an industrial environment, and in particular, to a stack light that includes a system for identifying the type of module present at each location within the stack configuration.
Stack lights are typically constructed of modular components that may be flexibly interconnected to produce stacks having varying combinations, orders, numbers, and configurations of modules. The modules may have various configurations and may include, for example, beacon modules emitting different colors of light, audible modules emitting different tones or sounds, or power modules receiving input power at one voltage and supplying power to the different modules at one or more different voltage levels. Although each module may provide a different function, they typically utilize identical mechanical and electrical connectors such that one module may be connected or stacked on another module. Unique base and/or terminating modules may be employed to provide a first or last module in the stack light, respectively.
A stack light may include different colored lamps and may be attached, or placed in close proximity, to operating industrial equipment to provide a visible indication of the equipment operating status. An audible module may also be provided to provide an audible indication of operating status. The tower structure provides visibility of the beacon lights over a range of angles and locations in the operating environment. Different colors of the lights allow multiple types of information to be communicated at a distance in a possibly noisy environment. For example, a red light may indicate a machine failure or emergency. A yellow light may indicate a warning such as an over-temperature or over-pressure condition. A green light may indicate proper machine operation. Further, the lights may be illuminated as a continuous or flashing light to provide still additional information related to the operation of the machine.
Control signals are provided to each module in the stack light to provide desired operation of the module. The control signals may be generated by an external controller, such as a programmable logic controller (PLC), or by wiring directly to devices on the controlled machine or process.
For example, a proximity switch may close and generate a signal when an access gate is closed. A complementary signal may be generated when the access gate is opened. The stack light may include a first beacon module with a green translucent housing and a second beacon module with a red translucent housing. The gate closed signal may be provided to the first beacon module and be intended to illuminate the green beacon module when the access gate is closed. The complementary, gate open signal may be provided to the second beacon module and be intended to illuminate the red beacon module when the access gate is open. Thus, an operator may readily identify whether the access gate is open or closed, which, in turn may indicate whether the machine is safe to operate.
While modularity of the stack light construction is intended to provide a customer with the ability to rapidly fabricate a wide variety of different stack light configurations out of readily available (stocked) components, the large number of configurations, however, can lead to an error in assembly. For example, because the modules are interchangeable, it is possible that the order in which the two exemplary beacon modules discussed above are switched during assembly. The gate open and closed signals, if wired to the correct terminals, would illuminate the incorrect beacons. As a result, the green beacon module would be illuminated when the access gate is open and the red beacon module is illuminated when the access gate is closed.
Thus, it would be desirable to provide a system to verify the identity of modules within a stack light.